drain to somewhere else other than the garage as I am building out the garage to use as a room. He ended up connecting the drain pan to the sewer in the wall next to the hot water heater as it has sinks on the other sides. He used a swing check valve:

to stop the sewer gas from going back into the water heater closet. My question ... is this sufficient to keep the sewer gas out? I have a feeling that its not and there should be some sort of P-Trap or something else to keep the gas out. I haven't been able to smell any sewer smell in the hot water heater closet yet but I am very concerned that it might be letting small amounts of gas through. Any help here would be much appreciated.

So it sounds like I need to get this looked at again. Can you give me a little more details on what indirect waste is and how you create a properly sized air gap? Is it a dangerous condition because gas can leak out into the house? I'm trying to get more details so if I do need this fixed I know what SHOULD be done

One additional question.. I should be able to smell the gas if its leaking right? I would think the swing check wouldn't stop the gas but I can't seem to smell anything. I wonder if the proper solution here would be to go through the wall to the sink on the other side and connect to it before the P Trap like the A/C units do. Would that be the proper solution or is there a way to fix it without doing that?

Depending on the situation, some drain lines don't really smell much, so no, you may not smell anything. Yes, this should be corrected, and if the guy is licensed and it was done with a permit, a call to the inspector would get fast action.

Again the point is that you want to see if there is a problem.
If the water heater is leaking you want it to dribble on the floor and piss you off enough to call a plumber.
That is the point! Do not route the drain from the drip pan to a hidden point do not hide any problems that may occour.

If there is a problem you want to know before it becomes dangerous!!!
Michael

Thanks for the reply! Can someone explain what an indirect drain is. I'm thinking of having it go to the bathroom drain before the P Trap ( Just like my AC unit does in a different bathroom). Is that an indirect drain like you are referring to?

The hot water heater is raised up fairly high off the floor that it could drain to the sink behind the wall where it is now. I'm not sure if that is what you refer to as an indirect drain though... and whether there is a carbon monoxide risk by having the drain go into the house like that.

There is no carbon monoxide in sewer gas. Actually, there is no danger whatever from sewer gas in the amounts that would issue from household drain pipes. It is merely unpleasant.
Were this not so, most plumbers would have died long ago. A water heater overflow outlet is not a drain, and should not be connected to the drain system. It is just an emergency overflow put in to limit damage caused by sudden water heater failure. It can discharge anywhere convenient and should not be hidden from sight.

AN indirect drain does not have a continuous connection, there is a gap between the outlet and the inlet oriented such that if the drain got plugged, there would be no direct connection between the two. think of your faucet for a sink...it is an indirect connection to the drain because it is high enough so that it can't make a 'direct' connection to the water that may be in the sink, and possibly suck contaminated water from the drain into the potable water system.

There may be two separate situations here. The drain pan CAN connect to the sink drain BEFORE the trap, although it is not a good idea to do so. The safety valve CANNOT empty into the drain pan because the pan's drain line is completely inadequate to handle the flow and WILL overflow within seconds of the valve activating, and CANNOT connect directly to the sewer system because of backflow and temperature considerations.

There is no carbon monoxide in sewer gas. Actually, there is no danger whatever from sewer gas in the amounts that would issue from household drain pipes. It is merely unpleasant.
Were this not so, most plumbers would have died long ago. A water heater overflow outlet is not a drain, and should not be connected to the drain system. It is just an emergency overflow put in to limit damage caused by sudden water heater failure. It can discharge anywhere convenient and should not be hidden from sight.

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Too many have died sticking their heads down into a newly opened septic tank, especially working on a pump in the outlet chamber, hanging by their knees upside down.

So the proviso is depends on where you are in the system. Methane also can make it up the main vent stack, which is why there are so many codes about distance to windows and such. Notice those big blowers at manholes that are being entered - not for comfort!

An example of an indirect drain is your washing machine that empties into an open standpipe. My water heater sets 4" off the basement floor on a concrete ledge at the end of an enclosed mop basin. The T/P drains into the basin as does the condensation from my furnace. The basin drains into a floor drain. The condensation from the furnace keeps the floor drain trap filled.